Fluid couplings, such as the type commonly found on the end of flexible hoses often use ball valves. The flow passage of a coupling or fitting houses the ball valves. Rotating the ball 90.degree. fully opens or closes the valves. Closing the ball valves before disconnecting the coupling provides low spillage or zero spillage of fluid, typically a hydrocarbon. When the couplings join together, each ball valve rotates to a flow permitting position. Before the couplings separate, each ball valve rotates to a flow preventing position. The ball valves interfit with one another so that a minimum volume of fluid is lost when the couplings separate.
One improvement in ball valve design has been a semi-spherical identical ball valves including flat exterior surfaces. When the ball valves are in the closed position, the flat surfaces are substantially coplanar. See U.S. Pat. No. 5,099,883. The patent shows a high flow, low spill valve coupling that reduces trapping fluid and spillage. As good as this flat coupling is, the two flat ball valves need a very small clearance or cavity between them to allow the ball valves to rotate. As small as this cavity may be, it fills with fluid that spills when the coupling disconnects. Tighter regulations are demanding less spillage. Some advances in technology have reduced spillage to 3 cc's.